Conventional forms of command and control (C2) in a high-end threat environment are suicide. As signature detection portfolios and long-range precision fires become more capable, the “flash to bang” between sensor and shooter only becomes more compressed. Potential adversaries of the United States are keenly aware of the C2 standard operating procedures used by U.S. military commanders both at sea and ashore and have tailored their tactical grids to exploit the habitual lack of effective signature management. This is no secret to the Sea Services. As early as 2016, the Marine Corps Operating Concept acknowledged that the future operating environment would be one in which to be detected is to be targeted and killed.1
That future has arrived. During combat in the ongoing Russo-Ukrainian war, Russian forces were able to locate, target, and destroy Ukrainian units by tracking cellphones carried by Ukrainian soldiers.2 In the unfolding
Armenia-Azerbaijan skirmishes, Armenian mechanized forces were easily detected in the electromagnetic spectrum and pummeled by Azerbaijani drones, loitering munitions, and multiple-launch rocket systems.3 And while many Chinese signature-detection capabilities remain undisclosed, former Seventh Fleet commander Vice Admiral Joseph Aucoin described them as “all encompassing.”4 Today, naval planners can abbreviate the premise of detection in the Marine Corps Operating Concept to a shorter, more chilling sentence: “To be detected is to be killed.”
This detection dilemma exacerbates any effort to prevent malign actors from attempting fait accompli ploys. Such strategies rapidly seize objectives and create antiaccess/ area-denial (A2/AD) situations that may prevent friendly governments from having the time or will to strike back, as this would exponentially escalate the situation and risk a spiral into greater conflict.5 The Russian annexation of Crimea in 2014 is a case in point, while the threat of a Chinese invasion of Taiwan is a potential case in the making.
To prevent great power competitors from executing such maneuvers, the 2017 National Security Strategy and 2018 National Defense Strategy (NDS) call on the military services to develop a strategy of deterrence by denial.6 To support this, the Navy and Marine Corps are pursuing expeditionary advanced base operations (EABO) and distributed maritime operations, which jointly mass effects while distributing forces. EABO aims to persist forward inside an adversary’s threat envelope, providing sea denial and setting conditions for the entry of follow-on naval forces into the area of operations.
EABO and distributed maritime operations are conceptually enabled by emerging communication, surveillance, reconnaissance, and fires technologies—all of which emit signatures that can be detected and targeted. Consequently, signature management is the critical vulnerability of not only EABO and distributed maritime operations, but also of sea denial and the deterrence by denial strategy that underwrites the NDS. Should naval expeditionary forces’ C2 systems at an EAB be detected or denied, the very premise of EABO and distributed maritime operations would be undermined. Thankfully, paths to achieving signature management are available through emerging techniques and technologies. These could validate EABO and distributed maritime operations and ensure an edge in competition and conflict.
Distributed maritime operations, EABO, and Deterrence by Denial
Distributed maritime operations and EABO are mutually supporting naval concepts that provide joint force commanders with sea denial and sea control and enable the flow of joint forces into an area of operations.
The Navy’s distributed maritime operations concept disaggregates naval forces afloat to deny adversaries a geographically concentrated target.7 At the same time, increasing capabilities of the sensors and C2 systems making up the naval tactical grid allow a geographically distributed naval task force to mass offensive capabilities.
The Marine Corps’ EABO concept facilitates distributed maritime operations by establishing EABs across littoral regions inside an adversary’s weapons engagement zone. EABs field sensors, shooters, and C2 systems that can target adversary vessels afloat and facilities ashore and also transmit targeting information to Navy platforms, extending the reach of the naval sensor-shooter kill chain.8 Adversaries will be aware of this threat, influencing their decision-making calculus toward deterrence and in favor of U.S. interests. Should deterrence fail, this distributed, survivable network of naval stand-in forces will mass effects, create openings for the entry of stand-in forces, facilitate full entry of the joint force into the operating area, and fight at sea and ashore to win decisively.9
Signature: EABO’s Critical Vulnerability
Any strategy that challenges a peer or near-peer competitor must assume risk, and EABO is no exception. EAB-hosted inside forces, while effectively holding a knife to an adversary’s throat, will by design be deployed within range of enemy precision fires systems. Forces operating inside an adversary’s weapons engagement zone are likewise within an adversary’s sensors’ range; a weapons engagement zone could just as well be defined as a weapons and sensors engagement zone.10
Deployed to key maritime terrain in the littorals, with weapons ready to silence A2/AD systems or sink enemy ships, naval stand-in forces must remain capable of C2 with their higher headquarters, as the command to fire will have, or arise from, strategic consequences. While the demand for uninterrupted C2 will only rise, these forces will have far less room to maneuver in the electromagnetic spectrum, as they will be within range of enemy shore-based, direction-finding systems and detectable by aviation and space-based surveillance systems.
This environment turns EABO into an operational game of hide-and-seek. Poor signature management is a death sentence for stand-in forces and will defeat the strategy they hope to employ. These forces must reduce their signatures to avoid detection and ensure C2 of combat systems is available at decisive moments by remaining unjammed and maintaining freedom of action in the electromagnetic spectrum.
Emerging tactics and technologies can be employed to overcome these signature challenges and mitigate the greatest risks to forces conducting EABO.
Revolutionize with Disruptive Techniques
The unique characteristics of the high-frequency (HF) radio band and the single-channel radio systems that operate on it make it extremely useful for communicating while avoiding detection. Tactical radios at higher frequency bands, such as very high frequency (VHF), ultra-high frequency (UHF), and satellite communications (SatCom), are easier to detect. HF systems have the right combination of network flexibility, range, and portability, which makes them the best choice for communications to support EABO.11 Still, vulnerabilities remain when using normal operating modes and procedures; if enemy direction-finding systems are scanning an area in which HF radios are transmitting, they will be detected.12 Thankfully, transmission techniques and signature-aware operating procedures can greatly reduces the likelihood of detection.
Low probability of intercept (LPI) is a method for operating HF radios that rapidly varies their power output and transmit frequencies and reduces the likelihood of detection.13 The principles behind HF-LPI are open source and require the operator’s tactical finesse. Particular methods used by the Sea Services are classified but known to some communicators and should be emphasized and practiced regularly.
The challenge is that whether HF-LPI techniques are employed by a unit, and to what level of proficiency that unit’s communicators train, are at the discretion of ship and unit commanders. An order from senior leaders to make a servicewide HF-LPI standard operating procedure available to the force, accompanied by an order to make it a mission-essential task, would ensure capability and proficiency across the Sea Services. Such an initiative would be simple and affordable to implement and would provide an asymmetric advantage over enemy direction-finding capabilities.
Automate Spectrum Modulation
Naval communicators can be trained to use these and other techniques today, but this is still extremely risky; efficacy depends on the skill and discipline of individual operators. Failure to establish C2 with HF-LPI could put on-scene commanders in a position either to increase their exposure in the electromagnetic spectrum to establish C2 or stay hidden within the spectrum while keeping themselves blind to the operational situation.
Automating HF-LPI and other emerging spectrum-modulation techniques not only would reduce signatures to acceptable levels, but also would remove the risk of human error. Direct sequence spread spectrum randomizes bit transmission and is commonly used in the commercial environment to support wireless networks. It is normally applied by compressing a relatively wider bandwidth spread of a signal to a narrower bandwidth, increasing the signal-to-noise ratio for ease of access. Reversing this process, however, would better conceal the signal, like a needle in the haystack.
Another option, frequency-hopping spread spectrum, rapidly moves a transmission across frequencies. It has been used in military radios for decades, but new variations offer enhanced protection. Adaptive frequency hopping is used by Bluetooth technologies to avoid crowded frequencies to maximize signal integrity, but it also could be used to avoid frequencies being scanned by adversaries. Automating these spectrum-modulation techniques would greatly reduce the likelihood of signal detection and interception.14
Nuke the Spectrum
While the previous options seek to “hide the needle in the haystack,” another option is to build a haystack around the needle. Instead of adhering to strict signature discipline that operates below the signature baseline of an already quiet sector (such as a remote island), planners could field a litany of emitters that deliberately transmit to confound adversaries monitoring the electromagnetic spectrum. If U.S. forces “nuked the spectrum,” adversaries would be unable to separate the signal from the noise and, in turn, be confronted by an unsolvable targeting dilemma.
Any method that artificially raises the electromagnetic spectrum baseline would effectively nuke the spectrum. The Sea Services can achieve this by pairing emitters with other initiatives that rapidly flood an operating area with various platforms. The Defense Advanced Research Project Agency’s (DARPA’s) Gremlins program provides low-cost swarms of interconnected, unmanned aerial systems launched from a larger aircraft.15 Similarly, the Office of Naval Research and Naval Sea Systems Command are developing a fleet of small, unmanned, interconnected attack boats.16
These programs and others are intended to provide cheap, expendable sensors and shooters, but with slight modifications, they also could raise the electromagnetic spectrum baseline and facilitate signature deception. Swarms engineered to transmit signals that technically and behaviorally imitate the C2 systems used by the naval stand-in force could provide on-demand signature protection for stand-in forces. These swarms also could be used as redundant nodes within the communications architecture that repeat, retransmit, and relay signals to further deceive adversaries. In other words, signals’ points of origin would be masked while increasing the robustness of the C2 architecture.
Interceptor and Jammer Rejection
A platoon of Marines on patrol in the forest will maintain stealth to the maximum extent possible, moving quietly and communicating with hand-and-arm signals to prevent detection. But when that platoon makes contact with the enemy, stealth goes by the wayside in favor of fire superiority and using the radio to coordinate combined arms.
The moment will come when naval stand-in forces must employ fires to achieve sea denial. At that moment, concealment within the electromagnetic spectrum will become infeasible and not a priority; signal integrity will be the critical requirement. C2 systems must be able to overcome the adversary’s efforts to jam signals on which stand-in forces depend. Emerging technologies have the potential to defeat enemy jamming.
DARPA’s Protected Forward Communications (PFC) program uses a structured system-engineering method to reinforce the strength of a signal such that it is highly resistant to jamming.17 Notably, PFC has the potential to protect internal and external communications. This would ensure C2 for EABO, whether it is the signal from a naval headquarters to the EAB to fire, from an operator to a system to fire, or from a sensor guiding that round onto target.
Similarly, the Hyper-Wideband Enabled Radio-Frequency Messaging (HERMES) system deploys multiple interceptor and jammer rejection techniques, such as processing gain, integrated filters, and active cancellation.18 HERMES also uses a broad spectral spreading that further challenges detection systems and increases interference resistance.19
Managing Signatures for Deterrence and Denial
Distributed maritime operations and EABO are the Sea Services’ bid to provide deterrence by denial. Sea denial provided by EAB-hosted stand-in forces will allow the Sea Services to puncture the A2/AD bubble, deter adversaries from attempting fait accompli operations, and better shape the strategic environment to suit the interests of the United States, its allies, and partners.
This strategy embraces the adage that “victory lies close to the opponent’s blade.” Naval stand-in forces must necessarily be placed within striking distance of enemy A2/AD systems, making signature management a critical requirement.
By applying disruptive tactics with emerging technologies, naval stand-in forces can persist forward while avoiding enemy detection. By acquiring, fielding, and employing appropriate systems while training naval communicators to hide in plain sight, EABO and distributed maritime operations can fulfill the promise of deterrence by denial. Signature management will ensure the Sea Services can prevent and, if necessary, win the wars of the future.
1. Headquarters Marine Corps, Marine Corps Operating Concept (Washington, DC: 2016).
2. Dustin Volz, “Russian Hackers Tracked Ukrainian Artillery Units Using Android Implant: Report,” Reuters, 22 December 2016, reuters.com/article/us-cyber-ukraine/russian-hackers-tracked-ukrainian-artillery-units-using-android-implant-report-idUSKBN14B0CU.
3. Michael Kofman and Leonid Nersisyan, “The Second Nagorno-Karabakh War, Two Weeks In,” War on the Rocks, 14 October 2020, warontherocks.com/2020/10/the-second-nagorno-karabakh-war-two-weeks-in/.
4. Mark Pomerleau, “Breaking Down China’s Electronic Warfare tactics,” C4ISRNet, 22 March 2017, c4isrnet.com/c2-comms/2017/03/22/breaking-down-chinas-electronic-warfare-tactics/.
5. Mike Gallagher, “State of (Deterrence by) Denial,” The Washington Quarterly 42, no. 2 (June 2019): 31–45.
6. National Security Strategy of the United States of America (December 2017), whitehouse.gov/wp-content/uploads/2017/12/NSS-Final-12-18-2017-0905.pdf.
7. CAPT Kevin Eyer, USN (Ret), and Steve McJessy, “Operationalizing Distributed Maritime Operations,” CIMSEC, 5 March 2019, cimsec.org/operationalizing-distributed-maritime-operations/39831.
8. Headquarters Marine Corps, “Expeditionary Advanced Base Operations,” U.S. Marine Corps Concepts and Programs, candp.marines.mil/Concepts/Subordinate-Operating-Concepts/Expeditionary-Advanced-Base-Operations/.
9. Jim Lacey, “The ‘Dumbest Concept Ever’ Might Just Win Wars,” War on the Rocks, 29 July 2019, warontherocks.com/2019/07/the-dumbest-concept-ever-just-might-win-wars/.
10. MAJ Brian Kerg, USMC, “Winning the Spectrum,” CIMSEC, 7 August 2020, cimsec.org/winning-the-spectrum-securing-command-and-control-for-marine-stand-in-forces/45122.
11. National Telecommunications and Information Administration, “Department of Defense Strategic Spectrum Plan,” NTIA (November 2007), ntia.doc.gov/files/ntia/publications/dod_strategic_spectrum_plan_nov2007.pdf.
12. National Urban Security Technology Laboratory, Radio Frequency Detection, Spectrum Analysis, and Direction Finding Equipment (New York: Department of Homeland Defense, 2019), 12.
13. G. Bark, “Power Control in an LPI Adaptive Frequency-hopping System for HF Communications,” HF Radio Systems and Techniques, Seventh International Conference, Conference Publication no. 441 (August 1997).
14. Syed Shah, “Assured Communications,” Milcom 2015 Presentation (October 2015).
15. Scott Wierzbanowski, “Gremlins,” DARPA, www.darpa.mil/program/gremlins.
16. Kris Osborn, “The U.S. Navy Is Building a Swarm ‘Ghost Fleet,’” The National Interest, 24 January 2019, nationalinterest.org/blog/buzz/us-navy-building-swarm-ghost-fleet-42372.
17. Paul Zablocky, “Protected Forward Communications,” DARPA, www.darpa.mil/program/protected-forward-communications.
18. Tom Rondeau, “Hyper-wideband Enabled RF Messaging,” DARPA, www.darpa.mil/program/hyper-wideband-enabled-rf-messaging.
19. DARPA Outreach Office, “The Incredible Loudness of Whispering,” DARPA, www.darpa.mil/news-events/2016-08-30.